Magnesium alloy

ABSTRACT

The present invention relates to a magnesium alloy based on 100% by weight of the total magnesium alloy, Al: 0.03 to 16.0% by weight, Mn: 0.015 to 1.0% by weight, Sc: 0.02 to 0.5% by weight, lanthanide rare earth element (RE): 0.03 to 2.0% by weight, and the balance Mg and inevitable impurities, wherein, the rare earth element (RE) comprise La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or a combination thereof.

TECHNICAL FIELD

One embodiment of the present invention relates to a magnesium alloy.

BACKGROUND

A magnesium alloy has the lowest specific gravity and excellent specificstrength and specific rigidity among practically available structurematerials and recently, has been increasingly demanded in automobilesand electronic products requiring lightness.

In addition, since the magnesium alloy has been suggested as a medicalbiodegradable implant, research on developing a magnesium material for asurgical implant for a bone fraction and a stent for a blood vessel/adigestive organ is being actively made.

Conventional research had been focused on a magnesium alloy for an autoengine, a gear part, or the like based on excellent castability ofmagnesium, but research on a magnesium alloy for processibility into anextruded material or a sheet material more variously applicable to wherelightness has recently been required is actively being made.

Most of magnesium alloys such as a magnesium-aluminum-based alloy, amagnesium-zinc-based alloy, a magnesium-tin-based alloy, and the likeshow a very high corrosion rate compared with competitive metal aluminumalloys, and this high corrosion rate plays a role of obstructingcommercial availability of the magnesium alloys as structural andmedical materials.

CONTENTS OF THE INVENTION Problem to be Solved

It is to provide a magnesium alloy.

Means to Solve the Problem

In one embodiment of the present invention, it is provided a magnesiumalloy comprising:

based on 100% by weight of the total magnesium alloy, Al: 0.03 to 16.0%by weight, Mn: 0.015 to 1.0% by weight, Sc: 0.02 to 0.5% by weight,lanthanide rare earth element (RE): 0.03 to 2.0% by weight, and thebalance Mg and inevitable impurities,

wherein, the rare earth element (RE) comprise La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or a combination thereof.

The rare earth element (RE) may be included in an amount of 0.1 to 1.0%by weight.

With respect to the total 100% by weight of the magnesium alloy, Zn:less than 5.0% by weight may be further included.

With respect to the total 100% by weight of the magnesium alloy, Zn: 0.1to 4.5% by weight may be further included.

With respect to the total 100% by weight of the magnesium alloy, Ca:2.0% by weight or less may be further included. More specifically, itmay be contained 0.5 to 2.0% by weight.

With respect to the total 100% by weight of the magnesium alloy, Y: 0.5%by weight or less may be further included. More specifically, it may becontained more than 0 and 0.3% by weight or less.

In another embodiment of the present invention, it is provided a methodfor producing a magnesium alloy including:

Preparing a molten metal comprising based on the total 100% by weight,Al: 0.03 to 16.0% by weight, Mn: 0.015 to 1.0% by weight, Sc: 0.02 to0.5% by weight, lanthanide rare earth element (RE): 0.03 to containing2.0% by weight, the balance Mg and inevitable impurities; and

manufacturing a cast material by casting the molten metal;

wherein, the rare earth element (RE) is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb or a combination thereof.

The molten metal may contain 0.1 to 1.0% by weight of the rare earthelement (RE).

With respect to the total 100% by weight of the molten metal, Zn: lessthan 5.0% by weight may be further included.

With respect to the total 100% by weight of the molten metal, Ca: 2.0%by weight or less may be further included. More specifically, Ca: 0.5 to2.0% by weight may be included.

With respect to the total 100% by weight of the molten metal, Y: 0.5% byweight or less may be further included.

After the step of producing a cast material by casting the molten metal,a step of rolling, extrusion, drawing, forging, or a combination of thecast material, may be further included.

The step of producing a cast material by casting the molten metal; maybe carried out in a temperature range of 600° C. to 800° C.

In another embodiment of the present invention, it is provided amagnesium alloy including 0.02 to 2% by weight of a rare earth element(RE), a balance of Mg, and unavoidable impurities with respect to 100%by weight of the total magnesium alloy.

The rare earth element may be Sc.

The magnesium alloy may be a binary alloy of Mg and Sc.

Alternatively, the magnesium alloy may be a ternary alloy of Mg—Sc—Mn,Mg—Sc—Ca, Mg—Sc—Y, Mg—Sc—Zn, or Mg—Sc—Sn.

The magnesium alloy may include a secondary phase particle that isSc—Si—Fe, Sc—Si, or a combination thereof.

The magnesium alloy may contain 0.02 to 0.5% by weight of Sc.

The magnesium alloy may contain 0.05 to 0.1% by weight of Sc.

The magnesium alloy may further contain Mn: 2.8% by weight or less. Morespecifically, it may further include Mn: more than 0 and 2.8% by weightor less. More specifically, it may further include Mn: 0.1 to 2.8% byweight.

The magnesium alloy may further include Ca: 0.1% by weight or less. Morespecifically, it may further contain Ca: more than 0 and 0.1% by weightor less.

The magnesium alloy may further include Y: 1% by weight or less. Morespecifically, it may further include Y: more than 0 and 1% by weight orless.

The magnesium alloy may further include Zn: 2.0% by weight or less. Morespecifically, it may further include Zn: more than 0 and 2.0% by weightor less. More specifically, it may further contain Zn: 0.1 to 2.0% byweight.

The magnesium alloy may further contain Sn: 5% by weight or less. Morespecifically, it may further contain Sn: more than 0 and 5% by weight orless.

In another embodiment of the present invention, it is provided a methodfor producing a magnesium alloy comprising:

preparing a molten metal containing 0.02 to 2% by weight of rare earthelements (RE), the balance Mg and inevitable impurities, based on thetotal 100% by weight; and producing a cast material by casting themolten metal. After the step of producing a cast material by casting themolten metal,

Rolling, extrusion, drawing, forging, or a combination thereof may befurther included for the cast material.

Effect

According to an embodiment of the present invention, a magnesium alloyhaving excellent corrosion resistance can be provided.

These magnesium alloys can be variously used as cast materials, rolledmaterials, extruded materials, drawn materials, forged materials, etc.that can be practically applied to industries requiring excellentcorrosion resistance.

BRIEF DESCRIPTION OF THE DRAWING

The file of this patent contains at least one drawing executed in color.Copies of this patent with color drawing(s) will be provided by thePatent and Trademark Office upon request and payment of the necessaryfee.

FIG. 1 is a scanning electron microscope photograph showing secondaryphase particles formed inside a rolled Mg-3 Al-0.3Mn-0.1Sc-1Zn alloy.

FIG. 2 is a scanning electron microscope photograph showing secondaryphase particles formed in a rolled Mg-3Al-0.3Mn-0.1Sc-1Zn-0.3Gd alloy.

FIG. 3 is a comparison data of the corrosion rate according to thescandium content.

FIG. 4 is a scanning electron microscope photograph showing secondaryphase particles formed inside the Mg casting material of Comparativeexample 1.

FIG. 5 is a scanning electron microscope photograph showing secondaryphase particles formed inside the Mg-0.05Sc cast material of Example 2.

FIGS. 6 and 7 are results of measuring a difference in voltaic potentialbetween the aforementioned secondary phase material and the magnesiummatrix.

FIG. 8 is a photograph of the surface of a magnesium cast materialaccording to an increase in Sc content.

SPECIFIC DESCRIPTION OF THE INVENTION

Advantages and features of the present invention and a method ofachieving them will become apparent with reference to the embodimentsdescribed below in detail together with the accompanying drawings.

However, the present invention is not limited to the embodimentsdisclosed below, and may be implemented in various different forms.

However, these embodiments are provided to complete the disclosure ofthe present invention and to fully inform the scope of the invention tothose of ordinary skill in the art to which the present inventionpertains.

The invention is only defined by the scope of the claims. The samereference numerals refer to the same elements throughout thespecification.

Accordingly, in some embodiments, well-known techniques have not beendescribed in detail in order to avoid obscuring interpretation of thepresent invention.

Unless otherwise defined, all terms (including technical and scientificterms) used in the present specification may be used as meanings thatcan be commonly understood by those of ordinary skill in the art towhich the present invention belongs.

When a part of the specification “comprise” a certain component, itmeans that other components may be further included rather thanexcluding other components unless specifically stated to the contrary.

Also, the singular form includes the plural form unless specificallystated in the text.

Hereinafter, two types of Mg alloy will be described. The first part isfor the Mg—Al alloy, and the second part is for the Al-free Mg alloy.

I. Mg—Al alloy

In one embodiment of the present invention, it is provided a magnesiumalloy comprising:

based on 100% by weight of the total magnesium alloy, Al: 0.03 to 16.0%by weight, Mn: 0.015 to 1.0% by weight, Sc: 0.02 to 0.5% by weight,lanthanide rare earth element (RE): 0.03 to 2.0% by weight, and thebalance Mg and inevitable impurities,

wherein, the rare earth element (RE) comprise La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or a combination thereof.

The reasons for limiting the components and compositions of themagnesium alloy are as follows.

First, aluminum contributes to an increase in the strength of the alloythrough solid solution strengthening and precipitation strengthening,and plays a role of improving corrosion resistance by improving thestability of the oxide film during corrosion.

Accordingly, when the amount of aluminum is too small, the effect ofincreasing the strength and improving the corrosion resistance may notbe expected.

On the other hand, if the content of aluminum is too high, the fractionof brittle particles containing aluminum may be excessive, resulting ina problem that the ductility of the alloy is weak.

Manganese contributes to an increase in the strength of the alloythrough solid solution strengthening and the like. In addition, byforming compound particles that absorb impurities in the alloy, it playsa role of improving the corrosion resistance of the magnesium alloy.

When manganese is included in too small an amount, the strength increaseand anti-corrosion improvement effects may be insufficient.

Even in a magnesium alloy containing scandium, manganese may have aneffect of improving the corrosion resistance.

However, if too much manganese is added in the magnesium alloycontaining scandium, the fraction of the particles containing manganeseis rather excessive and microgalvanic corrosion is rather promoted,thereby reducing corrosion resistance.

Accordingly, the upper limit of manganese may be limited as in theexemplary embodiment of the present invention.

Accordingly, 0.015 to 1.0% by weight of Mn may be included with respectto 100% by weight of the total magnesium alloy. Specifically, it may be0.015 to 0.6% by weight.

More specifically, when the manganese content exceeds 1.0% by weight,the above-described corrosion rate increases, and the effect ofimproving corrosion resistance according to the addition of rare earthelements may be insignificant.

Scandium plays a role in improving the corrosion resistance of magnesiumalloys by participating in changes in the electrochemical properties ofsecondary phase particles.

Accordingly, if the content of scandium is too small, the fraction ofthe secondary phase particles containing scandium is small, so it may bedifficult to expect the addition effect of scandium to improve corrosionresistance.

On the other hand, if the content of scandium is too high, the fractionof the particles containing scandium is excessive, which may lead toproblems of promoting microgalvanic corrosion and increasing alloyprices.

Rare earth elements can improve corrosion resistance by participating inchanges in electrochemical properties of secondary phase particles.

Specifically, in one embodiment of the present invention, the rare earthelement (RE) is a lanthanide rare earth element, such as La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Combinations of these may beincluded.

If the element is added among rare earth elements, the effect ofimproving corrosion resistance may be excellent.

More specifically, in one embodiment of the present invention, an effectof improving corrosion resistance may be further expected by addingscandium and the lanthanide rare earth element excluding scandium in theabove-described content range.

Specifically, when the content of the rare earth element is too small,the effect of improving corrosion resistance may be insignificant, andwhen the content of the rare earth element is too large, the alloymanufacturing cost may be excessively increased.

Thus, the weight range of the rare earth element may be 0.03 to 2.0% byweight. Specifically, it may be 0.1 to 2.0% by weight. Morespecifically, it may be 0.1 to 0.9% by weight.

Like aluminum, zinc plays a role of contributing to increasing strengthof the alloy through solid-dissolution reinforcement and precipitationreinforcement.

Accordingly, when zinc is included in too small amount, the strengtheffect may not be expected, and thus the alloy may not be used as astructural material.

On the contrary, when zinc is included in too large an amount,microgalvanic corrosion may be promoted due to an excessive fraction ofparticles including zinc.

Accordingly, an upper limit of zinc may be limited according to oneembodiment of the present invention.

Accordingly, with respect to the total 100% by weight of the magnesiumalloy, Zn may be included in less than 5% by weight. More specifically,it may be 4.5% by weight or less. Even more specifically, it may be 0.1to 4.5% by weight.

Calcium plays a role of increasing an ignition temperature of magnesium.

Accordingly, if the content of calcium is too small, the ignitiontemperature of the alloy is low, so it may be necessary to use anexpensive protective gas for suppressing ignition, and this may increasethe cost of manufacturing the alloy.

On the other hand, when the amount of calcium is too large, stresses maybe focused around particles during the hot machinery process due to anexcessive fraction of particles including calcium and thus cause acrack.

In addition, microgalvanic corrosion may be promoted because thefraction of particles containing calcium is excessive. Accordingly, theupper limit of calcium may be limited as in the exemplary embodiment ofthe present invention.

Accordingly, with respect to the total 100% by weight of the magnesiumalloy, Ca may be included in an amount of 2.0% by weight or less. Morespecifically, it may be in the range of 0.5 to 2.0% by weight.

As described above, by limiting the composition range of the components,a magnesium alloy excellent in corrosion resistance can be provided.

Yttrium, like calcium, increases the ignition temperature of magnesiumalloys.

Accordingly, when yttrium is added in too small an amount, an effect ofimproving anti-ignition may be insufficient due to a low ignitiontemperature.

On the other hand, when yttrium is added too large an amount, there maybe a problem of promoting microgalvanic corrosion and increasing analloy cost due to an excessive fraction of particles including yttrium.

In another embodiment of the present invention, it is provided a methodfor producing a magnesium alloy including:

Preparing a molten metal comprising based on the total 100% by weight,Al: 0.03 to 16.0% by weight, Mn: 0.015 to 1.0% by weight, Sc: 0.02 to0.5% by weight, lanthanide rare earth element (RE): 0.03 to containing2.0% by weight, the balance Mg and inevitable impurities; and

manufacturing a cast material by casting the molten metal;

wherein, the rare earth element (RE) is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb or a combination thereof.

The molten metal may further contain less than 5.0% by weight of Zn,based on the total 100% by weight. Specifically, it may be furtherincluded Zn: 0.1 to 4.5% by weight.

The molten metal may further include Ca: 2.0% by weight or less based onthe total 100% by weight. Specifically, it may be further included Ca:0.5 to 2.0% by weight.

The molten metal may further include Y: 0.5% by weight or less based onthe total 100% by weight. Specifically, it may be further included Y:0.3% by weight or less.

The reason for limiting the component and composition of the moltenmetal is the same as the reason for limiting the component andcomposition of the magnesium alloy described above, and thus will beomitted.

The step of producing a cast material by casting the molten metal; canbe carried out in a temperature range of 600° C. to 800° C.

More specifically, sand casting, gravity casting, pressure casting, lowpressure casting, dewaxing casting, thin plate casting, strip casting,single roll casting, continuous casting, electromagnetic casting,electromagnetic continuous casting, die casting, precision casting,freeze casting, spray casting, centrifugal casting, semisolid metalcasting, quenching casting, side extrusion casting, single belt casting,twin belt casting, shell mold casting, mouldless casting, 3D printing,or a combination thereof can be used to manufacture a cast material.However, it is not limited thereto.

After the step of producing a cast material by casting the molten metal,a process including rolling, extrusion, drawing, forging or acombination of the cast material may be further included.

This means that the cast material manufactured above can be furthersubjected to a later processing process. Thereby, the cast material maybe provided in the shape of a rolled material, an extruded material, adrawn material, a forged material, or a product.

At this time, the process including rolling, extrusion, drawing,forging, or a combination thereof is not specifically limited, and anymethod of processing after appropriate heat treatment is performed usinga cast material if necessary.

Hereinafter, it will be described in detail through examples. However,the following examples are only illustrative of the present invention,and the contents of the present invention are not limited by thefollowing examples.

Example

In the present Examples and Comparative Examples, a magnesium castmaterial including the components and compositions disclosed in Tables 1to 6 and a rolled magnesium material including the components andcompositions disclosed in Table 7 below were prepared.

More specifically, a cast material was manufactured by casting a moltenmagnesium metal containing Mg and unavoidable impurities including thecomponents and compositions disclosed in Tables 1 to 6 below.

In addition, a rolled material was manufactured using a magnesium castmaterial containing Mg and inevitable impurities including thecomponents and compositions disclosed in Table 7 below.

Accordingly, the corrosion rates according to the alloy components andcompositions of the Examples and Comparative examples were measured, andare shown in Tables 1 to 7.

<Casting Material Manufacturing Method>

Pure Mg (99.9%), Pure Al (99.9%), Pure Mn (99.9%), Pure Sc (99.9%), PureRE (99.9%), Pure Zn (99.9%), Pure Ca (99.9%), Pure Y (99.9%) was used.

To have these compositions shown in Tables 1 to 7 below, the Mg alloywas dissolved in a graphite crucible using a high frequency inductionmelting furnace.

Herein, in order to prevent oxidation of the obtained melt solutions, aSF₆ and CO₂ mixed gas was coated on the melt solutions to block the airfrom contacting the melts.

After dissolving, the molten metal is maintained at 750° C. for 10minutes, and then poured into a steel mold preheated to 200° C. at amelting temperature determined in the range of 650 to 750° C. dependingon the alloy component. The as-cast specimens were obtained as 80mm-high, 40 mm-wide, and 12 mm-thick.

<Method of Manufacturing Rolled Material>

The cast material was subjected to homogenization heat treatment at 420°C. for 1 hour and then surface-processed to a thickness of 8.5 mm.

During the rolling process, the temperature of the specimen wasmaintained at 350° C. throughout each rolling pass, and the rolling rolltemperature was set at 200° C. The rolling process was performed untilthe final specimen thickness reached 1 mm at a reduction rate of 20% perpass.

The manufactured rolled material was annealed at 345° C. for 1 hour.

<Method of Measuring Corrosion Rate>

Corrosion characteristics by seawater of Examples and Comparativeexamples were evaluated as follows.

After polishing the surface of the magnesium alloy cast according to theExamples and Comparative examples to the P1200 sandpaper step, themagnesium alloy was immersed in a 3.5% by weight NaCl solution equal tothe NaCl concentration in seawater. At this time, the immersion test wasperformed at 25° C. (room temperature).

More specifically, the magnesium alloy was immersed in a 3.5 wt % NaClsolution at room temperature for 72 hours, and a surface oxide layergenerated during immersion was removed using a 200 g/L chromic acid(CrO₃) solution.

As a result, the weight change before and after immersion was measured,and the corrosion rate (unit: mmpy) of the magnesium alloy was measuredthrough Equation 1 below.

Corrosion rate mm/year (mmpy)=8760 (h/year)×10 (mm/cm)×weight loss(g)/(specimen density (g/cm³)×immersion time (h)×exposed area(cm²))  [Equation 1]

TABLE 1 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—3Al—0.3Mn—0.1Sc 0Casting 1.20 example material Example Mg—3Al—0.3Mn—0.1Sc—0.3MM 0.3Casting 0.69 (0.3MM=0.15Ce—0.075La—0.045Nd—0.03Pr) material ExampleMg—3Al—0.3Mn—0.1Sc—1.0MM 1.0 Casting 0.45(1.0MM═0.5Ce—0.25La—0.15Nd—0.1Pr) material ExampleMg—3Al—0.3Mn—0.1Sc—0.01Ce 0.01 Casting 1.20 material ExampleMg—3Al—0.3Mn—0.1Sc—0.03Ce 0.03 Casting 1.19 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Ce 0.05 Casting 0.75 material ExampleMg—3Al—0.3Mn—0.1Sc—0.1Ce 0.1 Casting 0.98 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.43 material ExampleMg—3Al—0.3Mn—0.1Sc—1.0Ce 1.0 Casting 0.45 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Pr 0.05 Casting 0.53 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Pr 0.3 Casting 0.66 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Gd 0.05 Casting 0.48 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Gd 0.3 Casting 0.80 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Nd 0.05 Casting 0.56 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05La 0.05 Casting 0.60 material ExampleMg—3Al—0.3Mn—0.1Sc—0.5La 0.5 Casting 0.72 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Sm 0.05 Casting 1.09 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Sm 0.3 Casting 0.70 material ExampleMg—3Al—0.3Mn—0.1Sc—0.5Sm 0.5 Casting 0.73 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Ho 0.05 Casting 0.62 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Ho 0.3 Casting 0.54 material ExampleMg—3Al—0.3Mn—0.1Sc—0.5Ho 0.5 Casting 0.47 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Er 0.05 Casting 0.71 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Er 0.3 Casting 0.65 material ExampleMg—3Al—0.3Mn—0.1Sc—0.5Er 0.5 Casting 0.43 material ExampleMg—3Al—0.3Mn—0.1Sc—0.05Yb 0.05 Casting 1.05 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Yb 0.3 Casting 0.64 material ExampleMg—3Al—0.3Mn—0.1Sc—0.5Yb 0.5 Casting 0.57 material

TABLE 2 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—0.3Al—0.015Mn—0.02Sc 0Casting 5.23 example material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Ce0.03 Casting 4.24 material Comparative Mg—3Al—0.3Mn—0.1Sc 0 Casting 1.20example material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.43material Comparative Mg—6Al—0.3Mn—0.1Sc 0 Casting 0.77 example materialExample Mg—6Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.45 material ExampleMg—6Al—0.3Mn—0.1Sc—0.3Ce—0.3Y 0.3 Casting 0.37 material ComparativeMg—12Al—0.3Mn—0.1Sc 0 Casting 0.39 example material ExampleMg—12Al—0.3Mn—0.1Sc—0.1Ce 0.1 Casting 0.26 material ExampleMg—12Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.16 material ExampleMg—12Al—0.3Mn—0.1Sc—1.0Ce 1.0 Casting 0.14 material ExampleMg—12Al—0.3Mn—0.1Sc—2.0Ce 2.0 Casting 0.14 material ComparativeMg—15Al—0.3Mn—0.1Sc 0 Casting 0.38 example material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.14 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Pr 0.3 Casting 0.16 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Gd 0.3 Casting 0.14 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Nd 0.3 Casting 0.15 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3La 0.3 Casting 0.15 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Sm 0.3 Casting 0.13 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Ho 0.3 Casting 0.13 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Er 0.3 Casting 0.16 material ExampleMg—15Al—0.3Mn—0.1Sc—0.3Yb 0.3 Casting 0.14 material

TABLE 3 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—0.3Al—0.015Mn—0.02Sc 0Casting 5.23 example material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Ce0.03 Casting 4.24 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Pr 0.03Casting 3.41 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Gd 0.03Casting 3.56 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Nd 0.03Casting 3.69 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03La 0.03Casting 6.85 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Sm 0.03Casting 3.20 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Ho 0.03Casting 4.83 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Er 0.03Casting 3.62 material Example Mg—0.3Al—0.015Mn—0.02Sc—0.03Yb 0.03Casting 3.15 material Comparative Mg—3Al—0.3Mn—0.1Sc 0 Casting 1.20example material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.43material Comparative Mg—3Al—0.6Mn—0.1Sc 0 Casting 3.52 example materialExample Mg—3Al—0.6Mn—0.1Sc—0.3Ce 0.3 Casting 1.99 material ComparativeMg—3Al—1.0Mn—0.1Sc 0 Casting 3.95 example material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Ce 0.3 Casting 4.14 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Pr 0.3 Casting 2.93 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Gd 0.3 Casting 2.84 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Nd 0.3 Casting 3.27 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3La 0.3 Casting 4.59 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Sm 0.3 Casting 3.02 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Ho 0.3 Casting 2.92 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Er 0.3 Casting 4.61 material ExampleMg—3Al—1.0Mn—0.1Sc—0.3Yb 0.3 Casting 3.62 material

TABLE 4 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—3Al—0.3Mn—0.3Ce 0.3Casting 1.39 example material Comparative Mg—3Al—0.3Mn—0.1Sc 0 Casting1.20 example material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce 0.3 Casting 0.43material Comparative Mg—3Al—0.3Mn—0.3Sc 0 Casting 1.19 example materialExample Mg—3Al—0.3Mn—0.3Sc—0.3Ce 0.3 Casting 0.43 material ComparativeMg—3Al—0.3Mn—0.5Sc 0 Casting 0.47 example material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Ce 0.3 Casting 0.51 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Pr 0.3 Casting 0.52 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Nd 0.3 Casting 0.41 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Gd 0.3 Casting 0.43 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3La 0.3 Casting 0.50 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Sm 0.3 Casting 0.44 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Ho 0.3 Casting 0.53 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Er 0.3 Casting 0.44 material ExampleMg—3Al—0.3Mn—0.5Sc—0.3Yb 0.3 Casting 0.47 material

TABLE 5 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—3Al—0.3Mn—0.1Sc—1Zn 0Casting 1.30 example material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce—1Zn 0.3Casting 0.83 material Example Mg—3Al—0.3Mn—0.1Sc—0.3Pr—1Zn 0.3 Casting0.96 material Example Mg—3Al—0.3Mn—0.1Sc—0.3Gd—1Zn 0.3 Casting 0.85material Example Mg—3Al—0.3Mn—0.1Sc—0.3Nd—1Zn 0.3 Casting 0.73 materialExample Mg—3Al—0.3Mn—0.1Sc—0.3La—1Zn 0.3 Casting 1.01 material ExampleMg—3Al—0.3Mn—0.1Sc—0.3MM—1Zn 0.3 Casting 0.90(0.3MM═0.15Ce—0.075La—0.045Nd—0.03Pr) material ExampleMg—3Al—0.3Mn—0.1Sc—1.0MM—1Zn 1.0 Casting 0.90(1.0MM═0.5Ce—0.25La—0.15Nd—0.1Pr) material ComparativeMg—3Al—0.3Mn—0.1Sc—4Zn 0 Casting 1.53 example material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Ce—4Zn 0.3 Casting 1.07 material ComparativeMg—3Al—0.3Mn—0.1Sc—5Zn 0 Casting 1.41 example material ExampleMg—3Al—0.3Mn—0.1Sc—0.3Ce—5Zn 0.3 Casting 1.43 material

TABLE 6 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—3Al—0.3Mn—0.1Sc—1Zn 0Casting 1.30 example material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce—1Zn 0.3Casting 0.83 material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce—1Zn—0.5Ca 0.3Casting 0.56 material Example Mg—3Al—0.3Mn—0.1Sc—0.3Ce—1Zn—2.0Ca 0.3Casting 0.28 material

As can be seen from the above table, the composition ranges of aluminum,manganese, and scandium are the same as in the examples, but when therare earth element is not added, it can be seen that the corrosion rateis faster than when the rare earth element is added.

However, even when a rare earth element is added, it can be seen thatthere is no significant effect in improving the corrosion rate in thecase of the comparative example containing less than 0.03% by weight ofRE.

In addition, it can be seen that even when manganese and scandium arenot included, the corrosion rate is faster than in the examples.

It was possible to evaluate how much corrosion resistance was improvedaccording to the kind of rare earth elements, which are Ce, Pr, Nd, Gd,La, Sm, Ho, Er, Yb, or combinations thereof, respectively.

In the above table, the results for the alloy further containing Zn canalso be known. It was found that the corrosion resistance was improvedeven in the alloy containing Zn for improving mechanical properties dueto the use of Sc and RE elements.

In the above table, the results for the alloy further containing Ca canalso be known. It was found that the improved corrosion resistance wasmaintained even in the alloy containing Ca for improving the ignitionresistance due to the use of Sc and RE elements, and rather, thecorrosion resistance was slightly improved.

However, when the content of calcium is excessive, the fraction of theparticles containing calcium is excessive and cracks occur duringsintering, so the addition amount of Ca is limited to 2.0% by weight orless.

In the above table, the results for the alloy further containing Y canalso be known. It was found that the improved corrosion resistance wasmaintained even in the alloy containing Y for improving the ignitionresistance due to the use of Sc and RE elements, and rather, thecorrosion resistance was slightly improved.

However, when the content of yttrium is excessive, the fraction ofparticles containing yttrium is excessive, which promotes microgalvaniccorrosion and may lead to the cost of the alloy, so that the amount of Yadded was limited to 0.3% by weight or less.

Table 7 below is an evaluation result of a rolled material of amagnesium alloy prepared as a component of Examples and ComparativeExamples.

TABLE 7 Total weight Corrosion Lanthanide RE Specimen rate Division Nameof alloy (wt %) condition (mmpy) Comparative Mg—3Al—0.3Mn—0.1Sc—1Zn 0rolled 1.51 example material Example Mg—3Al—0.3Mn—0.1Sc—1Zn—0.3MM 0.3rolled 0.78 (0.3MM═0.15Ce—0.075La—0.045Nd—0.03Pr) material ExampleMg—3Al—0.3Mn—0.1Sc—1Zn—0.3Gd 0.3 rolled 0.81 material ExampleMg—12Al—0.3Mn—0.1Sc—0.3Ce 0.3 rolled 0.26 material

It was found that the specimen containing Al, Mn, and Sc according to anembodiment of the present invention and at the same time containing Ce,which is one of the rare earths, exhibited a considerably excellentcorrosion rate.

In addition, the properties of the alloy of the present invention wereconfirmed through SEM photographs.

FIG. 1 is a scanning electron microscope photograph showing secondaryphase particles formed inside a rolled Mg-3Al-0.3Mn-0.1Sc-1Zn alloy.Through this microstructure analysis, it can be seen that Al—Mn—Fe-basedparticles and Al—Mn—Sc particles containing impurity Fe are formed inthe rolled material.

FIG. 2 is a scanning electron microscope photograph showing secondaryphase particles formed in a rolled Mg-3Al-0.3Mn-0.1Sc-1Zn-0.3Gd alloy.When a rare earth element such as Gd is added to theMg-3Al-0.3Mn-0.1Sc-1Zn alloy through this microstructure analysis,double particles in the form of a core-shell, which is that theparticles containing impurity Fe are located in the center and theAl—Mn-RE particles are located outside, are formed.

In general, Fe-containing particles are known to activate microgalvaniccorrosion in magnesium alloys due to their high electrochemicalpotential. As described above, since particles present in the core ofdouble particles cannot cause hydrogen reduction reactions in acorrosive environment. These particles do not activate microgalvaniccorrosion, which may improve the corrosion resistance of the alloy.

II. Al-Free Mg Alloy

In one embodiment of the present invention, a magnesium alloy including0.02 to 2% by weight of a rare earth element (RE), a balance of Mg andinevitable impurities is provided with respect to 100% by weight of thetotal magnesium alloy material.

The reasons for limiting the components and compositions of themagnesium alloy material are as follows.

Scandium plays a role in improving the corrosion resistance of themagnesium alloy material by participating in the change of theelectrochemical properties of the secondary phase particles.

Accordingly, if the content of scandium is too small, the degree ofchange in the electrochemical properties of the secondary phaseparticles containing scandium is small, so it may be difficult to expectthe addition effect of scandium to improve corrosion resistance.

On the other hand, if the content of scandium is too high, the fractionof the particles containing scandium is excessive, which may lead toproblems of accelerating microgalvanic corrosion and an increase inalloy material prices. In addition, if the content of scandium isexcessive, irregularities may occur on the surface of the castingmaterial.

Rare earth elements can improve corrosion resistance by participating inchanges in electrochemical properties of secondary phase particles.Specifically, in one embodiment of the present invention, the effect ofimproving corrosion resistance can be further expected by addingscandium in the above-described content range of the rare earth elementRE.

If the content of the rare earth element is too small, the effect ofimproving corrosion resistance may be insignificant, and if too much,the alloy manufacturing cost may be excessively increased.

Thus, the weight range of the rare earth element may be 0.02 to 2% byweight. Specifically, it may be 0.05 to 0.1% by weight.

Manganese contributes to an increase in the strength of the alloythrough solid solution strengthening and the like. In addition, byforming compound particles that absorb impurities in the alloy, itcontributes to improving the corrosion resistance of the magnesiumalloy.

Accordingly, when the content of manganese is too small, the effect ofincreasing strength and improving corrosion resistance may beinsignificant. Even in a magnesium alloy material containing scandium,there may be an effect of improving the corrosion resistance ofmanganese.

However, when too much manganese is added in the magnesium alloymaterial containing scandium, the fraction of the particles containingmanganese is excessive, and microgalvanic corrosion is rather promoted,thereby reducing corrosion resistance.

In addition, when the proportion of the particles containing manganeseis excessive, the elongation may decrease during sintering deformationof the alloy. Accordingly, the upper limit of manganese may be limitedas in the exemplary embodiment of the present invention.

Accordingly, with respect to the total 100% by weight of the magnesiumalloy material, it may contain more than 0 and 2.8% by weight of Mn.Specifically, it may be 0.1 to 2.8% by weight.

More specifically, when the manganese content exceeds 2.8% by weight,the effect of improving corrosion resistance due to the addition of therare earth element may be insignificant and the elongation may decrease.

Calcium plays a role of increasing an ignition temperature of magnesium.

Accordingly, if the content of calcium is too small, the ignitiontemperature of the alloy is low, so it may be necessary to use anexpensive protective gas for suppressing ignition, and this may increasethe cost of manufacturing the alloy.

On the other hand, when the amount of calcium is too large, stresses maybe focused around particles during the hot machinery process due to anexcessive fraction of particles including calcium and thus cause acrack.

In addition, microgalvanic corrosion may be promoted because thefraction of particles containing calcium is excessive. Accordingly, theupper limit of calcium may be limited as in the exemplary embodiment ofthe present invention.

Thus, with respect to the total 100% by weight of the magnesium alloymaterial, Ca may be included in an amount of 0.1% by weight or less.More specifically, it may be in the range of more than 0 and 0.1% byweight or less.

As described above, by limiting the composition range of the components,a magnesium alloy material excellent in corrosion resistance can beprovided.

Yttrium, like calcium, increases the ignition temperature of magnesiumalloys.

Accordingly, when yttrium is added in too small an amount, an effect ofimproving anti-ignition may be insufficient due to a low ignitiontemperature.

On the other hand, when yttrium is added too large an amount, there maybe a problem of promoting microgalvanic corrosion and increasing analloy cost due to an excessive fraction of particles including yttrium.

Zinc plays a role in increasing the strength of the alloy through solidsolution strengthening and precipitation strengthening.

Accordingly, when zinc is included in too small amount, the strengtheffect may not be expected, and thus the alloy may not be used as astructural material.

On the contrary, when zinc is included in too large an amount,microgalvanic corrosion may be promoted due to an excessive fraction ofparticles including zinc.

Accordingly, the upper limit of zinc may be limited as in the exemplaryembodiment of the present invention.

Thus, with respect to the total 100% by weight of the magnesium alloymaterial, it may further include Zn: 2.0% by weight or less. Morespecifically, it may further include more than 0 and 2.0% by weight orless. More specifically, it may further contain 0.1 to 2.0% by weight.

Like zinc, tin (Sn) plays a role in increasing the strength of the alloythrough solid solution strengthening and precipitation strengthening.When tin is added to the magnesium alloy, strength can be expected dueto the presence of the Mg₂Sn precipitated phase, but microgalvaniccorrosion may be promoted due to an increase in the fraction of theprecipitated phase.

When the magnesium alloy contains more than 5% by weight of tin,microgalvanic corrosion is promoted due to the presence of an excessiveprecipitated phase, and thus the effect of improving corrosionresistance due to the addition of Sc may be offset.

Accordingly, the magnesium alloy may further include Sn: 5% by weight orless. More specifically, it may further contain more than 0 and 5% byweight or less.

The magnesium alloy according to an embodiment of the present inventionmay be a binary alloy of Mg and Sc.

In this alloy, secondary phase particles that are Sc—Si—Fe, Sc—Si, or acombination thereof may be included. Although it will be described inmore detail in the examples to be described later, since theelectrochemical potential of these secondary phase particles is similarto that of magnesium, the electrochemical potential difference with themagnesium matrix decreases, so that microgalvanic corrosion can besuppressed.

In another embodiment of the present invention, it is provided a methodfor producing a magnesium alloy comprising:

preparing a molten metal containing 0.02 to 2% by weight of rare earthelements (RE), the balance Mg and inevitable impurities, based on thetotal 100% by weight; and producing a cast material by casting themolten metal. The reason for limiting the component and composition ofthe molten metal is the same as the reason for limiting the componentand composition of the magnesium alloy described above, and thus will beomitted.

The step of producing a cast material by casting the molten metal; canbe carried out in a temperature range of 600° C. to 800° C.

More specifically, sand casting, gravity casting, pressure casting, lowpressure casting, dewaxing casting, thin plate casting, strip casting,single roll casting, continuous casting, electromagnetic casting,electromagnetic continuous casting, die casting, precision casting,freeze casting, spray casting, centrifugal casting, semisolid metalcasting, quenching casting, side extrusion casting, single belt casting,twin belt casting, shell mold casting, mouldless casting, 3D printing,or a combination thereof can be used to manufacture a cast material.However, it is not limited thereto.

After the step of producing a cast material by casting the molten metal,a process including rolling, extrusion, drawing, forging or acombination of the cast material may be further included.

This means that the cast material manufactured above can be furthersubjected to a later processing process. Thereby, the cast material maybe provided in the shape of a rolled material, an extruded material, adrawn material, a forged material, or a product.

At this time, the process including rolling, extrusion, drawing,forging, or a combination thereof is not specifically limited, and anymethod of processing after appropriate heat treatment is performed usinga cast material if necessary.

Hereinafter, it will be described in detail through examples. However,the following examples are only illustrative of the present invention,and the contents of the present invention are not limited by thefollowing examples.

Experimental Example

Alloy production method: pure Mg (99.9%), pure Sc (99.9%), was used.

To make them have the composition shown in Table 8 below, the Mg alloywas dissolved in a graphite crucible using a high frequency inductionmelting furnace.

At this time, to prevent oxidation of the molten metal, a mixed gas ofSF₆ and CO₂ was applied on the top of the molten metal to block contactwith the atmosphere.

After melting, the molten metal was maintained at 750° C. for 10minutes, and an as-cast specimen having a height of 80 mm, a width of 40mm, and a thickness of 12 mm was prepared using a steel mold preheatedto 200° C.

Corrosion Rate Evaluation Method and Results: In order to evaluate thecorrosion characteristics of a total of 10 magnesium alloy specimensaccording to Table 8, the surface of the magnesium alloy specimen wasfirst polished to the P 1200 sanding step, and then an immersion testwas performed on the magnesium alloy specimen in NaCl solution of 3.5%by weight maintained at a temperature of 25° C.

That is, the previously prepared magnesium alloy specimen is immersed ina 3.5 wt % NaCl solution at 25° C. for 72 hours, and the surface oxidelayer generated during immersion is removed using a 200 g/L chromic acid(CrO₃) solution. Then, the weight is measured before and afterimmersion. The change of weight was measured and then the corrosion rate(unit: mmpy) of the specimen was calculated according to the followingequation, and the results are shown in Table 8 below.

Corrosion rate (mmpy)=8760 (h/year)×10 (mm/cm)×weight loss (g)/(specimendensity (g/cm³)×immersion time (h)×exposed area (cm²))

TABLE 8 Content Corrosion of Sc Specimen rate Division Name of alloy (wt%) condition (mmpy) 1 Comparative Mg — Casting 4.93 example 1 material 2Example 1 Mg—0.02Sc 0.02 Casting 1.35 material 3 Example 2 Mg—0.05Sc0.05 Casting 0.36 material 4 Example 3 Mg—0.1Sc 0.1 Casting 0.48material 5 Example 4 Mg—0.2Sc 0.2 Casting 1.25 material 6 Example 5Mg—0.5Sc 0.5 Casting 1.46 material 7 Example 6 Mg—1.0Sc 1.0 Casting 1.21material 8 Comparative Mg—1.5Sc 1.5 Casting 1.36 example 2 material 9Comparative Mg—2.0Sc 2.0 Casting 1.28 example 3 material 10 ComparativeMg—3.0Sc 3.0 Casting 1.30 example 4 material

As shown in Table 8, it can be seen that the corrosion resistance ofmagnesium is improved due to the addition of Sc.

However, if more than an appropriate level of Sc is included, a problemmay occur in the quality of the manufactured specimen.

FIG. 8 is a photograph of the surface of a magnesium cast materialaccording to an increase in Sc. It can be seen that as the Sc contentincreased, irregularities occurred on the magnesium surface.

FIG. 3 is a comparison data of the corrosion rate according to thescandium content.

Scandium contained in the magnesium alloy plays a role of improving thecorrosion resistance of the magnesium alloy by forming a compoundcontaining impurities.

If the content of scandium is too small, the effect of improvingcorrosion resistance may be insignificant. If the content of scandium istoo high, the fraction of the particles containing scandium isexcessive, which may cause a problem of promoting galvanic corrosion.

The microstructures of Comparative examples and Examples were observedthrough FIGS. 4 and 5 below.

FIG. 4 is a scanning electron microscope photograph showing secondaryphase particles formed inside the Mg casting material of Comparativeexample 1.

Through such microstructure analysis, it can be seen that Fe—Si-basedparticles containing impurity Fe are formed in commercial magnesiummaterials.

FIG. 5 is a scanning electron microscope photograph showing secondaryphase particles formed inside the Mg-0.05Sc cast material of Example 2.

FIGS. 6 and 7 below are results of measuring the difference in voltaicpotential between the above-described secondary phase material and themagnesium matrix.

More specifically, the voltaic potential difference between thesecondary phase compound and the magnesium matrix present in the alloysof Comparative examples 1 and Example 2 was measured using a scanningKelvin probe force microscopy (SKPFM) equipment of NT-MDT. The resultsare shown in FIGS. 6 to 7.

FIG. 6 is a SKPFM map showing the difference in voltaic potentialbetween the secondary phase particles formed in the Mg casting materialof Comparative example 1 and the magnesium matrix, and a result of aline profile thereof.

FIG. 7 is a SKPFM map showing the difference in voltaic potentialbetween the secondary phase particles formed in the Mg-0.05Sc castmaterial of Example 2 and the magnesium matrix, and the result of a lineprofile thereof.

As in the above embodiment, when Sc element having an electrochemicalpotential similar to that of magnesium is additionally included in thesecondary phase compound particles, the electrochemical potentialdifference between the particles and the magnesium matrix decreases,thereby suppressing microgalvanic corrosion.

Table 9 below shows the corrosion rate evaluation data of a ternaryalloy further including Mn and Ca as additional elements added to theMg—Sc alloy.

The specific experimental method is the same as the experimental examplein Table 8, and the content of the alloy component was variouslyadjusted.

TABLE 9 Content Corrosion of Sc Specimen rate Name of alloy (wt %)condition (mmpy) Mg—0.1Mn — Casting 4.90 material Mg—0.1Mn—0.05Sc 0.05Casting 0.75 material Mg—0.5Mn — Casting 18.11 material Mg—0.5Mn—0.05Sc0.05 Casting 0.61 material Mg—1.5Mn — Casting 5.98 materialMg—1.5Mn—0.05Sc 0.05 Casting 0.53 material Mg—2.8Mn — Casting 0.49material Mg—2.8Mn—0.05Sc 0.05 Casting 0.44 material Mg—0.1Ca — Casting1.32 material Mg—0.1Ca—0.05Sc 0.05 Casting 0.61 material Mg—0.3Ca —Casting 0.38 material Mg—0.3Ca—0.05Sc 0.05 Casting 1.13 materialMg—0.5Ca — Casting 4.73 material Mg—0.5Ca—0.05Sc 0.05 Casting 18.71material

In the case of a ternary alloy further containing Mn, it can beconfirmed that the corrosion resistance is improved due to the additionof Sc until the content of Mn becomes 2.8% by weight.

However, when Mn was 2.8% by weight, it was confirmed that the degree ofimprovement in corrosion resistance according to the addition of Sc wasnegligible.

In the case of a ternary alloy further containing Ca, it can be seenthat the corrosion resistance is improved by adding Sc only when thecontent of Ca is 0.1% by weight or less.

When the Ca content was 0.3% by weight, it was confirmed that thecorrosion resistance was rather poor.

Table 10 shows corrosion rate evaluation data of a ternary alloy furtherincluding Y and Zn as additional elements in the Mg—Sc alloy.

The specific experimental method is the same as the experimental examplein Table 8, and the content of the alloy component was variouslyadjusted.

TABLE 10 Content Corrosion of Sc Specimen rate Name of alloy (wt %)condition (mmpy) Mg—0.1Y — Casting 19.02 material Mg—0.1Y—0.05Sc 0.05Casting 6.83 material Mg—0.5Y — Casting 20.50 material Mg—0.5Y—0.05Sc0.05 Casting 4.74 material Mg—1Y — Casting 2.93 material Mg—1Y—0.05Sc0.05 Casting 1.58 material Mg—2Y — Casting 1.70 material Mg—2Y—0.05Sc0.05 Casting 5.42 material Mg—4Y — Casting 6.59 material Mg—4Y—0.05Sc0.05 Casting 9.57 material Mg—0.1Zn — Casting 0.95 materialMg—0.1Zn—0.05Sc 0.05 Casting 0.55 material Mg—1Zn — Casting 0.87material Mg—1Zn—0.05Sc 0.05 Casting 0.54 material Mg—2Zn — Casting 1.30material Mg—2Zn—0.05Sc 0.05 Casting 1.30 material

In the case of the ternary alloy further containing Y, it can beconfirmed that the corrosion resistance is improved due to the additionof Sc until the content of Y becomes 1% by weight.

However, it was confirmed that when Y became 2% by weight, the corrosionresistance was rather poor.

In the case of a ternary alloy further containing Zn, it can beconfirmed that the corrosion resistance is improved due to the additionof Sc until the content of Zn becomes 2% by weight.

However, it was confirmed that when the Zn was 2% by weight, the degreeof improvement in corrosion resistance according to the addition of Scbecame insignificant.

Table 11 shows the corrosion rate evaluation data of a ternary alloyfurther containing Sn as an additional element in the Mg—Sc alloy.

The specific experimental method is the same as the experimental examplein Table 8, and the content of the alloy component was variouslyadjusted.

TABLE 11 Content Corrosion of Sc Specimen rate Name of alloy (wt %)condition (mmpy) Mg—5Sn — Casting 5.77 material Mg—5Sn—0.05Sc 0.05Casting 5.54 material

In the case of the ternary alloy further containing Sn, it can beconfirmed that the corrosion resistance is improved due to the additionof Sc until the content of Sn is 5% by weight.

However, it was confirmed that when Sn was 5% by weight, the degree ofimprovement in corrosion resistance depending on whether Sc was addedwas insignificant.

The embodiments of the present invention have been described above withreference to the accompanying drawings, but those of ordinary skill inthe art to which the present invention pertains can be implemented inother specific forms without changing the technical spirit or essentialfeatures. You can understand.

Therefore, it should be understood that the embodiments described aboveare illustrative and non-limiting in all respects. The scope of thepresent invention is indicated by the claims to be described laterrather than the detailed description, and all changes or altered formsderived from the meaning and scope of the claims and their equivalentconcepts should be interpreted as being included in the scope of thepresent invention.

1. A magnesium alloy comprising: based on 100% by weight of the totalmagnesium alloy, Al: 0.03 to 16.0% by weight, Mn: 0.015 to 1.0% byweight, Sc: 0.02 to 0.5% by weight, lanthanide rare earth element (RE):0.03 to 2.0% by weight, and the balance Mg and inevitable impurities,wherein, the rare earth element (RE) comprise La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or a combination thereof.
 2. Themagnesium alloy of claim 1, wherein, the rare earth element (RE) iscomprised 0.1 to 1.0% by weight.
 3. The magnesium alloy of claim 1, themagnesium alloy further comprises: with respect to the total 100% byweight of the magnesium alloy, Zn: less than 5.0% by weight.
 4. Themagnesium alloy of claim 3, the magnesium alloy further comprises: withrespect to the total 100% by weight of the magnesium alloy, Zn: 0.1 to4.5% by weight.
 5. The magnesium alloy of claim 1, the magnesium alloyfurther comprises: with respect to the total 100% by weight of themagnesium alloy, Ca: 2.0% by weight or less.
 6. The magnesium alloy ofclaim 1, the magnesium alloy further comprises: with respect to thetotal 100% by weight of the magnesium alloy, Y: 0.5% by weight or less.7. A magnesium alloy comprising: based on 100% by weight of the totalmagnesium alloy, 0.02 to 2% by weight of rare earth element (RE), thebalance Mg and unavoidable impurities.
 8. The magnesium alloy of claim7, the rare earth element is Sc.
 9. The magnesium alloy of claim 7,wherein, the magnesium alloy is a binary alloy consisting of Mg and Sc.10. The magnesium alloy of claim 7, wherein, the magnesium alloy isternary alloy comprising Mg—Sc—Mn, Mg—Sc—Ca, Mg—Sc—Y, Mg—Sc—Zn, orMg—Sc—Sn.
 11. The magnesium alloy of claim 7, wherein, the magnesiumalloy comprises a secondary phase particle which is Sc—Si—Fe, Sc—Si, ora combination thereof.
 12. The magnesium alloy of claim 7, wherein, themagnesium alloy comprises 0.05 to 0.1% by weight of Sc.
 13. Themagnesium alloy of claim 7, wherein, the magnesium alloy furthercomprises Mn: 2.8% by weight or less.
 14. The magnesium alloy of claim7, wherein, the magnesium alloy further comprises Ca: 0.1% by weight orless.
 15. The magnesium alloy of claim 7, wherein, the magnesium alloyfurther comprises Y: 1% by weight or less.
 16. The magnesium alloy ofclaim 7, wherein, the magnesium alloy further comprises Zn: 2% by weightor less.
 17. The magnesium alloy of claim 7, wherein, the magnesiumalloy further comprises Sn: 5% by weight or less.